Touch panels are used in various fields. In a personal digital assistant such as smartphones or tablet PCs, a touch panel is provided below a surface protection panel made of glass or the like. Below the touch panel, a polarizing film and a display are provided in the stated order.
In such a personal digital assistant, for the purpose of improving the transparency, luminance, and contrast on the display screen to enhance the visibility, an interlayer space between the surface protection panel and the touch panel and an interlayer space between the touch panel and the polarizing film are filled with a filling material that has a smaller difference in refractive index with these components than air does.
As interlayer filling materials for a touch panel, acrylic adhesives are often used from the standpoint of transparency, adhesiveness, and coating properties (see Patent Literature 1, for example).
A touch panel laminate produced using an acrylic adhesive as an interlayer filling material, however, tends to have cracks or breakage in a surface protection panel or a glass substrate. Along with the recent trend of downsizing, thinning, or weight reduction of a personal digital assistant, thinning of a surface protection panel, a glass substrate, or a filling material has been promoted. Such a thin touch panel laminate, however, is more likely to have cracks or breakage.